1. Field of the Invention
The present invention relates to a lid frame for a nuclear fuel assembly shipping container and a shipping container for nuclear fuel assemblies, capable of safely transporting a nuclear fuel assembly to a nuclear power plant, etc. after the nuclear fuel assembly has been produced.
2. Description of the Related Art
In general, nuclear fuel such as enriched uranium or mixed oxide needs to be transported between various places, for instance a place where they are concentrated, a fuel rod producing place, and so on. For this transporting stage, the fuel is typically shaped like a small pellet.
When stored, this fuel requires a constant level of thermal insulation and structural strength to comply with international standards, and the control of their criticality is a main concern, and the mass of enriched fuel in a shipping container should be strictly restricted such that a dangerous situation does not arise. Due to this requirement, the volume of fuel that can be transported in a shipping container of a certain volume is under strict restrictions.
As a result, numerous shipping containers for transporting the nuclear fuel assembly have been disclosed. As shown in FIG. 1, such a shipping container is designed so that a plurality of clamps 10 are installed separately apart from each other by predetermined intervals so as to clamp a nuclear fuel assembly 1. In this case, it is impossible to safely protect the nuclear fuel assembly from external shocks caused by falling, penetration, and so on.
To compensate for this problem, as shown in FIG. 2, the shipping container may be designed so that a pair of clamping frames 20 are coupled to opposite long sides of the shipping container with the nuclear fuel assembly disposed therebetween, and are formed in a completely closed shape so that the nuclear fuel assembly is clamped. The strength of the shipping container itself including the clamping frames 20 must be reliable, and thus the containers are typically formed of a metal material. In this way, when the clamping frames 20 are formed in a completely closed shape, the nuclear fuel assembly can be safely protected, but the shipping container itself becomes very heavy, and the cost of production is increased as well.
Furthermore, in the case of conventional nuclear fuel assembly shipping containers with clamps that have the same size, since the positions of the spacer grids are different for each type of nuclear fuel assembly, a lid frame in which the clamps are disposed so as to correspond to the positions of the spacer grids should be used to transport different types of nuclear fuel assemblies. Accordingly, a different lid frame should be provided depending on the type of nuclear fuel assembly.